Fossil records mechanisms

The escape of the trace elements back to the water column could be prevented by burial, thereby preserving a sediment record. However, such fossilized enrichments might be difficult to detect the surface sediments commonly have extremely low densities, and thus comprise very little material. On burial, we can expect that any enrichment will be strongly diluted by the normal underlying and overlying sediment. There are, however, some potential examples in the sediment of Lake Baikal (Boyle et al., 1998), where frequent small turbidity flows provide an ideal mechanism for burying the surface enrichments. 

TEM observations document the presence of distinct areas of modulated microstructure in fossil and Recent brachiopod shells. This is the first record of modulated texture in extant skeletal carbonate. There are unresolved differences of opinion regarding the underlying mechanism of formation of modulated microstructures. Although, most modulated microstructure has been associated with diagenesis, the presence of the modulated structure in Recent brachiopods eliminates a diagenetic environment as a requirement for the formation of the texture in brachiopods. Furthermore, electron microprobe measurements indicate that the calcite studied is composed of low-magnesium calcite. Thus, no major cation substitutions, such as excess Mg+ in the lattice, are responsible for the modulated microstructures in brachiopod calcite. The two most likely explanations for modulated microstructure in brachiopod calcite... 

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